This invention relates to electrical couplings, connectors and components for such couplings or connectors.
Electrical connectors and couplings are usually made of metal, or include metal components, in order to provide strength and electrical conduction properties, such as for screening or grounding purposes. These metal components contribute a significant part of the overall mass of the connector. This can create problems in applications where it is important for weight to be kept to a minimum, such as in aircraft, and can increase the risk of vibration damage. It has previously been proposed that various metal components be replaced by components made of plastics materials, which may be electrically conductive where this is necessary. An effective way of making a plastics component electrically conductive is to plate it with a metal, such as described in GB 2344703. There is, however, a problem with plated plastics components that connect with another component in a toothed or similarly sharply pointed region, if the component is exposed to lightning strike. The high current flow produced by the lightning generates an electric field that is more intense at the pointed region and may cause delamination of the plating from the plastics substrate.
It is an object of the present invention to provide an alternative connector, coupling and component for such a connector or coupling.
According to one aspect of the present invention there is provided a coupling including a first cylindrical member of an electrically-insulative material plated with an electrically-conductive material and arranged to lock against rotational movement relative to a second member, the second member having a ring of sharp-edged locking teeth at its rear end, the coupling including an annular member of an electrically-conductive material disposed axially between the first and second members, the annular member having a ring of sharp-edged locking teeth at its forward end arranged to engage the teeth at the rear end of the second member, and the forward end of the first member and the rear end of the annular member each having a ring of smoothly rounded teeth that engage one another to prevent relative rotation between the first and annular members.
The first member is preferably of a plastics material and the sharp-edged teeth are preferably substantially triangular. The annular member may be of a metal, such as aluminium and may be plated with a metal. Preferably, the annular member and the first member are both plated with the same metal.
According to another aspect of the present invention there is provided an electrical connector backshell assembly including an outer metal nut threaded internally towards its forward end such that it can engage a screw thread on the outside of a connector front end assembly, an internal assembly within the nut for restraining rotation of the backshell assembly when fitted on the front end assembly, the internal assembly including a cylinder towards the rear of the assembly and a shorter annular member towards the forward end of the assembly, the cylinder being of a plastics material plated with a metal and having a series of smoothly rounded teeth at its forward end, and the annular member being of a metal and having at its rear end a series of smoothly rounded teeth shaped to engage with the teeth on the cylinder and having at its forward end a series of triangular teeth shaped to engage triangular teeth around the rear end of the front end assembly.
According to a further aspect of the present invention there is provided an electrical connector including a backshell assembly according to the above other aspect of the invention.
According to a fourth aspect of the present invention there is provided an internal assembly for use in an electrical coupling for restraining rotation of components of the coupling, the internal assembly including a cylinder and a shorter annular member located at the forward end of the cylinder, the cylinder being of a plastics material plated with a metal and having a series of smoothly rounded teeth at its forward end, and the annular member being of a metal and having at its rear end a series of smoothly rounded teeth shaped to engage the teeth on the cylinder and having at its forward end a series of triangular teeth shaped to engage triangular teeth around an engaging component of the coupling.
According to a fifth aspect of the present invention there is provided a coupling including an internal assembly according to the above fourth aspect of the invention.
An electrical connector according to the present invention, will now be described, by way of example, with reference to the accompanying drawings.